It is common practice for a rolling mill roll to comprise a roll body, a pair of necks at opposite axial ends to support that roll upon bearings of the mill stand and at one axial end, a roll stub or wobbler which is not of fully circular cross section and which can be engaged in a coupling box or sleeve of the head of a flexible coupling head spindle, for the driving of the roll, i.e. the transmission of torque between the coupling box and the roll stub.
The term "flexible coupling" as here used, is intended to refer primarily to couplings which include a shaft having so called "universal" joints at opposite ends and which are connected between the drive motor and the wobbler or stub of the roll for driving same.
A typical flexible coupling spindle is the universal joint type of spindle which has Hooke's joints or Hooke's couplings at opposite ends thereof. It is also possible to provide another type of universal coupling, for example, a toothed coupling of the type in which an externally toothed gear type member engages in an internally toothed gear type member but these members are so shaped that they need not be perfectly aligned axially to transfer torque therebetween.
The spindle head and the roll stub have mutually fitting surfaces when the roll stub is received in the coupling box, capable of transmitting torque therebetween and wear plates may be inserted between such surfaces with certain tolerances, for example, an interference fit or a sliding clearance to permit torque transmission. The latter case is preferred to facilitate mounting of the parts which must fit together.
Thus, while a certain play is frequently desirable to permit mounting of the assembly and connection of the roll stub with the coupling box or a similar sleeve, the system has the drawback that the wear plates are subjected to rapid wear and there are sudden jumps in the load applied to the system and hence in the operation of the mill which can detrimentally effect the quality of the products produced.